JP7266956B2 - Gas generant composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gas generant composition used in gas generators for automobile airbags.

Airbags and seatbelt pretensioners are employed as safety devices for automobile passengers. The operating principle of an airbag is that a sensor that detects the impact caused by a traffic accident sends an electric signal to the gas generator, which instantly burns the gas generating agent to generate gas, and the gas pressure inflate the airbag to prevent collision. It works to soften the impact on the occupant due to The same is true for seat belt pretensioners. When a vehicle collision is detected by a sensor, an electric signal is sent to the gas generator. A seat belt winding mechanism is operated to increase the restraining force of the seat belt to protect the occupant. The first performance required for gas generators used in automobile safety devices is to generate a necessary and sufficient gas pressure within a desired period of time.

The number of gas generators for airbags mounted on vehicles is increasing year by year. Therefore, there is an increasing demand for stable and reliable operation of gas generators over a long period of time. In particular, there is a concern that the physical properties and quality of the gas generating agent filled in the gas generator may be deteriorated by heat, so further improvement is required.

As a method of improving the heat resistance of the gas generating agent, there is a method of reducing the content of alkali metal alkaline earth metal (Patent Document 1). There is also a method of using a combination of a cellulose derivative and a polymeric plasticizer (Patent Document 2), and a method of using a carboxymethyl cellulose salt having a viscosity of 1,000 mPa·s or more (Patent Document 3).

Japanese Patent Application Laid-Open No. 2003-321293 Japanese Patent Application Laid-Open No. 2008-260658 JP 2016-160152 A

An object of the present invention is to provide a gas generant composition having excellent heat resistance.

The present inventors have made intensive studies to achieve the above object, and found that by using guanidine nitrate as a fuel component, a basic metal nitrate as an oxidizing agent component, a carboxymethyl cellulose salt as a binder agent, and an additive, The inventors have found that the heat resistance is remarkably improved, and have completed the present invention. The present invention is as follows.

(1) guanidine nitrate, a basic metal nitrate as an oxidizing agent component, and a carboxymethyl cellulose salt as a binder agent, and further selected from the group consisting of magnesium silicate, magnesium aluminometasilicate, magnesium oxide, and calcium carbonate; A gas generant composition comprising one or more additives.
(2) The gas generant composition according to (1), further comprising potassium perchlorate as the oxidant component.
(3) The guanidine nitrate content is 40 to 50% by mass, the basic metal nitrate content is 30 to 40% by mass, and the potassium perchlorate content is 5 to 15% by mass. The gas generant composition according to (2), wherein the carboxymethylcellulose salt is 1 to 9% by mass, and the additive is 1 to 10% by mass.
(4) A gas generator containing the gas generating composition according to any one of (1) to (3).

The gas generating agent of the present invention is selected from the group consisting of magnesium silicate, magnesium aluminometasilicate, magnesium oxide and calcium carbonate in the gas generating agent containing guanidine nitrate, basic metal nitrate and carboxymethyl cellulose salt as main components. A gas generating agent having excellent heat resistance can be obtained by further using one or more of these additives.

The details of the present invention are described below. The present invention contains guanidine nitrate, contains a basic metal nitrate, contains a carboxymethyl cellulose salt, and further contains an additive selected from the group consisting of magnesium silicate, magnesium aluminometasilicate, magnesium oxide, and calcium carbonate. It relates to gas generant compositions containing one or more.

The gas generant composition of the present invention contains guanidine nitrate as a fuel component. Since guanidine nitrate contains oxygen in its molecule, it is possible to reduce the amount of oxidizing agent to be compounded, and it has good thermal stability. Furthermore, it is expected to be low in cost and high in gasification rate during combustion. There are merits.

In the present invention, guanidine nitrate is preferably in the form of powder or granules because it is easy to handle, and its 50% particle size is preferably 3 to 80 μm, more preferably 5 to 50 μm. If the 50% particle size of guanidine nitrate is too large, the strength of the gas generant composition compact will decrease, while if it is too small, pulverization costs a lot. In the present invention, the 50% particle size means the 50% particle size based on the number of measured particles, and can be measured by, for example, a laser diffraction/scattering method.

The content (blending ratio) of guanidine nitrate in the gas generating agent composition of the present invention is preferably 20 to 60% by mass, more preferably 40 to 50% by mass. If the guanidine nitrate content (compounding ratio) is less than 20% by mass, the number of moles of gas generated per 100 g of the gas generating composition tends to decrease, and the excess oxygen tends to increase the generation of nitrogen oxides. On the other hand, if the content of guanidine nitrate (blended ratio) exceeds 60% by mass, the oxidizing agent component becomes insufficient, and a large amount of harmful carbon monoxide tends to be generated.

In the present invention, other nitrogen-containing organic compounds may coexist as fuel components. The nitrogen-containing organic compound is not particularly limited, and nitrogen-containing organic compounds commonly used in gas generating compositions for gas generators for vehicle occupant safety devices can be suitably used. Examples that are preferably used include guanidine or its derivatives, triazole or its derivatives, tetrazole or its derivatives, bitriazole or its derivatives, bitetrazole or its derivatives, azodicarbonamide or its derivatives, hydrazine or its derivatives, and hydrazide derivatives. are mentioned.

More specifically, 5-oxo-1,2,4-triazole, tetrazole, 5-aminotetrazole, aminotetrazole nitrate, nitroaminotetrazole, bitetrazole (5,5′-bi-1H-tetrazole), 5, 5′-bi-1H-tetrazolediammonium salt, azobistetrazole, 5,5′-azobistetrazole diguanidinium salt, guanidine, nitroguanidine, cyanoguanidine, triaminoguanidine nitrate, aminoguanidine nitrate, biuret, azodicarbonate Amide, carbohydrazide, carbohydrazide nitrate complex, oxalic acid hydrazide, hydrazine nitrate complex, ammine complex and the like are preferably mentioned. Among these nitrogen-containing organic compounds, tetrazole derivatives, bitetrazole derivatives and guanidine derivatives are preferred because they are inexpensive, highly reactive and relatively easy to handle, and nitroguanidine, bitetrazole, azobistetrazole and 5-amino Tetrazole is more preferred.

The present invention contains basic metal nitrates as oxidizing agents. Specific examples of the basic metal nitrate include basic copper nitrate, basic cobalt nitrate, basic zinc nitrate, basic magnesium nitrate, basic iron nitrate and the like. Among these, basic copper nitrate is particularly preferred because of its low combustion temperature and good thermal stability.

The mixing ratio of the basic metal nitrate in the present gas generant varies depending on the types and amounts of the guanidine nitrate used and the binder agent and additives described later, but is usually 25 to 75% relative to the gas generant composition. It is preferably in the range of 30 to 50% by mass, and more preferably in the range of 30 to 50% by mass in order to reduce the concentrations of carbon monoxide and nitrogen oxides in the generated gas.

The above basic metal nitrate is preferably in the form of powder or granules because it is easy to handle, and its 50% particle size is preferably 1 to 80 μm, more preferably 1 to 50 μm. If the 50% particle size of the basic metal nitrate is too large, the strength of the gas generant composition molded article will be reduced. On the other hand, if the particle size of the powder is too small, it may be difficult to uniformly mix it with the fuel component. In addition, there is also the problem that the preparation of small particle size basic metal nitrates requires a great deal of cost for pulverization.

The gas generant composition of the present invention may further contain nitrates and perchlorates as co-oxidants. The nitrates are alkali metal nitrates, alkaline earth metal nitrates and ammonium nitrate, and sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate and the like can be used. Ammonium nitrate may be phase-stabilized ammonium nitrate added with potassium salt or copper salt. As the perchlorate, sodium perchlorate, potassium perchlorate, ammonium perchlorate and the like can be used.

These nitrates and perchlorates may be used singly or in combination of two or more.

As an oxidizing agent, a preferred co-oxidizing agent used together with a basic metal nitrate is strontium nitrate, and a mixed oxidizing agent of basic copper nitrate and strontium nitrate is preferably used. Potassium perchlorate is also preferable, and it is preferable to use a mixed oxidizing agent of basic copper nitrate and potassium perchlorate.

When a co-oxidizing agent is used, the mixing ratio (w/w) of the basic metal nitrate and the co-oxidizing agent is preferably 10:1 to 1:10, more preferably 5:1 to 1:5. be.

The gas generant composition of the present invention comprises a carboxymethylcellulose salt. The combustion characteristics of the gas generating agent are affected by the molded shape of the gas generating agent. Carboxymethyl cellulose salt is a binder agent that imparts moldability and shape retention in order for the gas generating agent to exhibit the desired combustion characteristics. It has the function of maintaining the combustion performance by keeping the shape of the molded body of the agent. Moreover, when carboxymethyl cellulose salt is used as the binder, generation of harmful gases such as carbon monoxide and nitrogen oxides can be significantly suppressed.

As carboxymethylcellulose salts used in the present invention, sodium salts, potassium salts, magnesium salts, calcium salts, ammonium salts and the like can be used. Among them, sodium salts and ammonium salts are preferred.

The present invention may contain other binder agents such as carboxymethyl cellulose salts as binder agents. Other binder agents can be used without any particular limitation as long as they do not significantly adversely affect the combustion behavior of the gas generant composition. For example, celluloses such as hydroxyethyl cellulose, hydroxypropyl methyl cellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, nitrocellulose, microcrystalline cellulose, polysaccharide derivatives such as guar gum and starch, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, etc. Water-soluble organic binders such as water-soluble synthetic polymers are preferred. In addition, inorganic binders such as molybdenum disulfide, synthetic hydrotalcite, acid clay, talc, bentonite, diatomaceous earth, kaolin, silica and alumina can also be used. Since the gas generating agent composition of the present invention is suitable for preparation of a gas generating agent by extrusion molding using water as a medium, a water-soluble binder is preferably used as the binder to be used in combination. It is preferred to use polysaccharide derivatives, water-soluble synthetic polymers.

The content of the binder agent in the gas generant composition of the present invention is preferably 0.1 to 10% by mass, more preferably 1 to 8% by mass. If the content of the binder agent is high, the breaking strength of the molded body can be increased, but the number of carbon elements and hydrogen elements in the composition increases, and carbon monoxide gas, which is a product of incomplete combustion of carbon elements, concentration increases, the quality of generated gas is lowered, and combustion may be inhibited. For this reason, it is preferable to use the minimum amount that can maintain the shape of the gas generant composition. In particular, when the content of the binder agent exceeds 10% by mass, it is necessary to increase the relative abundance of the oxidizing agent component, and the relative abundance of the fuel component in the gas generant composition decreases. practical application may become difficult.

The gas generant composition of the present invention contains an additive for improving heat resistance. The additive is one or more additives selected from the group consisting of magnesium silicate, magnesium aluminometasilicate, magnesium oxide and calcium carbonate.

The content of the additive in the gas generant composition of the present invention is preferably 0 to 15% by mass, more preferably 0.5 to 15% by mass. It is particularly preferred to use a content of 4 to 10% by weight. If the content of the additive is high, problems such as deterioration in combustion performance and an increase in the amount of residue generated by combustion occur.

The gas generant composition of the present invention may further contain additives commonly used in gas generants, such as slag forming agents, lubricants and combustion modifiers.

The slag-forming agent is an additive that enables easy filtration of combustion residue generated after combustion of the gas generant composition, and is added for the purpose of preventing release to the outside of the inflator. Specific examples of the slag forming agent include natural minerals such as silicon nitride, silicon carbide, silicon dioxide, silicates, aluminum oxide, titanium oxide, acid clay and clay.

When a slag forming agent is used in the present invention, the content in the gas generating agent composition is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass. If the content of the slag forming agent is high, the combustibility is lowered and the number of moles of generated gas is lowered, so there is a possibility that the occupant protection performance may not be sufficiently exhibited.

Lubricants are added for the purpose of improving the mixability and fluidity of the raw material components during the preparation of the gas generant composition. Specific examples of the lubricant include graphite, magnesium stearate, zinc stearate, calcium stearate, sodium stearate, boron nitride, highly dispersed silica (silicon dioxide), talc and the like. Among these, highly dispersed silica (silicon dioxide) has the function of suppressing sticking and aggregation during raw material mixing and uniformly dispersing and mixing, and has the effect of maintaining the particle size characteristics and actions of each component. Especially useful.

When a lubricant is used in the present invention, the content of the lubricant in the gas generating composition is preferably 0.1 to 5% by mass, more preferably 0.1 to 2% by mass. If the content of the lubricant is high, there is a possibility that the combustibility is lowered, the number of moles of generated gas is decreased, and the concentration of carbon monoxide in the generated gas is increased.

Specific examples of combustion modifiers include metal oxides such as iron oxide, nickel oxide, copper oxide, zinc oxide, manganese oxide, chromium oxide, cobalt oxide, molybdenum oxide, vanadium oxide, tungsten oxide, copper hydroxide, hydroxide Examples include metal hydroxides such as cobalt, zinc hydroxide and aluminum hydroxide, carbons such as activated carbon powder, graphite and carbon black.

When a combustion modifier is used in the present invention, the content of the combustion modifier in the gas generating composition is preferably 10% by mass or less, more preferably 5% by mass or less.

The gas generant composition of the present invention is preferably used as a molded body having a suitable shape. Hereinafter, the shaped body of the gas generating composition is also referred to as a gas generating agent. The gas generating agent of the present invention can be molded into various shapes according to the combustion performance and combustion characteristics of the gas generator.

The shape of the gas generating agent of the present invention is not particularly limited, and includes pellets, discs, spheres, rods, cylinders, cylinders, confetti, tetrapods, and the like. The molded body may be non-porous or perforated such as single-hole or multi-hole (for example, single-hole cylindrical or multi-hole cylindrical). Further, the pellet-shaped or disc-shaped molded body may have one or more projections on one side or both sides thereof. The shape of the protrusions is not particularly limited, and examples thereof include cylindrical, cylindrical, conical, and polygonal pyramid shapes.

Examples of the method for molding the gas generating agent of the present invention include a pressure molding method and an extrusion molding method.

First, a method for producing a molded body of the gas generating agent of the present invention by pressure molding will be exemplified. When molding the gas generant composition into tablets, pellets or discs by pressure molding, various optional additives such as fuel components, oxidizer components, and additives are mixed in a V-type mixer, rocking mixer, or the like. Mix in a dry mixer. At the time of mixing, by dispersing and interposing the spheres in the mixture of the components, the powder of the components receives the force of the spheres in detail, so that the components are uniformly dispersed in the composition. It is desirable to use a mixer such as a rocking mixer that rotates and oscillates in order to obtain a gas generant composition in which each component is more uniformly dispersed. A solution containing a binder (binder solution) is added to the obtained gas generant composition (powder), and the gas generant composition is granulated using a wet granulator such as a stirring granulator. . The amount of the binder solution to be added cannot be generalized, but it can be added in an amount of 1 to 100% by mass with respect to the mixed powder.

After that, heat treatment is performed at 80 to 100° C. to obtain granules. If the water content of the granules after the heat treatment exceeds 1%, the fluidity may decrease and the pressure molding in the next step may not be performed stably, so the water content in the granules should be 1% by mass or less. , preferably 0.5% by mass or less.

The granules are then pressed into the desired shape on a rotary tablet press. At the time of pressure molding, it is possible to add a commonly used lubricant such as magnesium stearate in the range of 0.1 to 5% by mass. The press-molded compact can be used as a gas generating agent after being heat-treated at 100-110° C. for 5-20 hours. The water content in the gas generating agent after heat treatment is desirably 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.3% by mass or less.

On the other hand, when producing a molded product of the gas generant composition of the present invention by an extrusion molding method, various optional additives such as a fuel component, an oxidizing agent component, a binder agent, an additive and a combustion modifier are mixed in a mixer. 1 to 100% by mass of water and/or an organic solvent are added to the obtained mixed powder and sufficiently kneaded to obtain a viscous wet agent. Thereafter, the wet agent is passed through a die capable of being extruded into a desired shape, and the extrudate is appropriately cut. The extruded body is a columnar body, and a more preferable shape is a long columnar shaped body.

Thereafter, the extruded body is heat-treated at a temperature of 50 to 150° C. for about 5 to 50 hours to obtain a molded body of the gas generant composition that hardly changes with time.

In the manufacturing method by extrusion molding, since the molded body containing 10 to 20% by mass of water is heat-treated, it is necessary to heat-treat at a low temperature for a long time. In particular, this heat treatment is extremely effective in meeting the severe heat aging test of 107° C.×400 hours. The heat treatment time may be arbitrarily set as long as the heat treatment is performed until the water content of the resulting gas generating agent becomes 1% by mass or less. When heat treatment is performed at a temperature of 50 to 150° C., heat treatment is generally insufficient for less than 5 hours, and heat treatment for more than 5 hours is meaningless, but the heat treatment time depends on the shape of the gas generating agent. It should be set appropriately according to the size and size. However, if the heat treatment temperature exceeds 80° C. and water is rapidly evaporated, air bubbles will form in the compact, resulting in insufficient strength of the compact and pulverization of the gas generating agent, causing abnormal combustion. Therefore, a primary heat treatment is performed at 50 to 70° C. to reduce the water content in the gas generating agent to 7% or less, preferably 5% or less, and then a secondary heat treatment is performed at 80 to 150° C. to reduce the water content in the gas generating agent. It is desirable to carry out a stepwise heat treatment so as to reduce the water content of 1% by mass or less, preferably 0.5% by mass or less.

The gas generating agent of the present invention is used by loading it into a gas generator. A suitable gas generator is an inflator used for airbag deployment. Therefore, the present invention also includes an air bag inflator using the gas generating agent. The airbag inflator of the present invention is not particularly limited as long as it is an inflator that is normally mounted on a vehicle.

[Example 1]
44.1 parts by weight of guanidine nitrate, 36.9 parts by weight of basic copper nitrate, 10.0 parts by weight of potassium perchlorate, 5.0 parts by weight of magnesium silicate, 25 when made into a 1% (w/w) aqueous solution 4.0 parts by mass of carboxymethyl cellulose sodium salt having a viscosity of 3,340 mPa s measured with a Brookfield viscometer at ° C. was mixed with a rocking mixer, and 20 parts by mass of deionized water and 3 parts by mass of deionized water were mixed with a kneader. of ethanol was added and uniformly kneaded. An extruder equipped with a die is used to form a strand, which is taken up by a take-up belt and sent out between the forming gears. and cut. Then, it was dried at 55° C. for 8 hours and then at 110° C. for 8 hours to obtain the gas generating agent of Example 1.

[Example 2]
Guanidine nitrate 44.1 parts by mass, basic copper nitrate 36.9 parts by mass, potassium perchlorate 10.0 parts by mass, magnesium aluminometasilicate 5.0 parts by mass, 1% (w/w) aqueous solution 4.0 parts by mass of carboxymethylcellulose sodium salt having a viscosity of 3,340 mPa s measured with a Brookfield viscometer at 25 ° C. is mixed with a rocking mixer, and 20 parts by mass of deionized water and 3 parts by mass of ethanol was added and uniformly kneaded. An extruder equipped with a die is used to form a strand, which is taken up by a take-up belt and sent out between forming gears. and cut. Then, it was dried at 55° C. for 8 hours and then at 110° C. for 8 hours to obtain the gas generating agent of Example 2.

[Example 3]
44.1 parts by weight of guanidine nitrate, 36.9 parts by weight of basic copper nitrate, 10.0 parts by weight of potassium perchlorate, 5.0 parts by weight of magnesium oxide, 25 ° C. when made into a 1% (w / w) aqueous solution 4.0 parts by mass of carboxymethylcellulose sodium salt having a viscosity of 3,340 mPa s as measured by a Brookfield viscometer is mixed with a rocking mixer, and 20 parts by mass of deionized water and 3 parts by mass of deionized water are mixed with a kneader. of ethanol was added and uniformly kneaded. An extruder equipped with a die is used to form a strand, which is taken up by a take-up belt and sent out between the forming gears. and cut. After that, it was dried at 55° C. for 8 hours and then at 110° C. for 8 hours to obtain the gas generating agent of Example 3.

[Example 4]
44.1 parts by weight of guanidine nitrate, 36.9 parts by weight of basic copper nitrate, 10.0 parts by weight of potassium perchlorate, 5.0 parts by weight of calcium carbonate, 25°C when made into a 1% (w/w) aqueous solution 4.0 parts by mass of carboxymethylcellulose sodium salt having a viscosity of 3,340 mPa s as measured by a Brookfield viscometer is mixed with a rocking mixer, and 20 parts by mass of deionized water and 3 parts by mass of deionized water are mixed with a kneader. of ethanol was added and uniformly kneaded. An extruder equipped with a die is used to form a strand, which is taken up by a take-up belt and sent out between forming gears. and cut. After that, it was dried at 55° C. for 8 hours and then at 110° C. for 8 hours to obtain the gas generating agent of Example 4.

[Comparative example]
Guanidine nitrate 46.8 parts by weight, basic copper nitrate 39.2 parts by weight, potassium perchlorate 10.0 parts by weight, 1% (w / w) aqueous solution measured at 25 ° C. with a B-type viscometer 4.0 parts by mass of carboxymethylcellulose sodium salt having a viscosity of 3,340 mPa s was mixed with a rocking mixer, and 20 parts by mass of deionized water and 3 parts by mass of ethanol were added to the outside and mixed uniformly with a kneader. . An extruder equipped with a die is used to form a strand, which is taken up by a take-up belt and sent out between forming gears. and cut. Then, it was dried at 55° C. for 8 hours and then at 110° C. for 8 hours to obtain a gas generating agent of Comparative Example.

[Test Example] Evaluation of Heat Resistance 10 g each of the gas generating agents of Examples 1 to 4 and Comparative Example were filled in a sealed container having an internal volume of 22.3 cc, and placed in a constant temperature bath at 110°C. After 800 hours, 1,200 hours, and 2,000 hours, the sealed container was taken out from the constant temperature bath, and the weight change rate of the filled gas generating agent was measured.
The heat resistance was evaluated from the weight loss rate after the heat resistance test for 2,000 hours according to the following evaluation criteria. Table 1 shows the test results.
○: Weight reduction rate is less than 5% △: Weight reduction rate is 5% or more and less than 9% ×: Weight reduction rate is 9% or more

From the results of the test examples, it was clarified that Examples 1 to 4 reduced the weight loss rate compared to Comparative Example.

Claims (4)

guanidine nitrate, a basic metal nitrate as an oxidizing agent component, a carboxymethyl cellulose salt as a binder agent, and an additive selected from the group consisting of magnesium silicate, magnesium aluminometasilicate, magnesium oxide and calcium carbonate. A gas generant composition comprising at least one species,
The content of the guanidine nitrate is 40 to 50% by mass, the content of the basic metal nitrate is 30 to 40% by mass, the carboxymethylcellulose salt is 0.1 to 10% by mass, and the addition A gas generant composition containing 4 to 10% by mass of the agent. 2. The gas generant composition according to claim 1, wherein said additive is magnesium oxide and/or calcium carbonate. 3. The gas generant composition according to claim 1, further comprising potassium perchlorate as the oxidant component. A gas generator containing the gas generant composition according to any one of claims 1 to 3.